Review of the new BMW 330d Convertible

In some respects, the cars we drive today have changed surprisingly little in the last 100 years. In others, they've altered dramatically from the stage they were at only a few decades ago. A motorist from the turn of the 20th century relocated to the early stages of this one would recognise the four-wheeled boxes we travel in and the principals behind their internal combustion engines. A car owner time-warped here from the 1980s, on the other hand, might well smirk at the concept of a diesel convertible and gasp at the idea of a 245bhp one with a folding metal roof. BMW's 330d Convertible is a car that's very much of its time.

The convertible could be the ultimate expression of automotive frivolity, especially in Britain where having a roof on your car always seems that much more crucial thanks to our idiosyncratic weather patterns. The diesel engine, on the other hand, is much more of a solid citizen. Tell people you drive a diesel and they'll narrow their eyes and nod sagely, elevating you in their estimations as they do so. Diesel drivers are perceived to have weighed up the pros and cons, maybe done a few calculations, and arrived at a level-headed buying decision. Convertible owners, it's often suspected, woke up with a hangover one sunny morning and rushed down to the dealership on a whim. As a result, a diesel convertible might appear something of a paradox but the BMW 330d Convertible manages to balance the diesel Yin with the convertible Yang just so.

BMW's standard 3.0-litre six-cylinder diesel is no longer the star of the 3 Series engine range that it was when it first arrived on the scene. That honour goes to the twin turbo version of the powerplant as fitted to the 335d models. The 330d Convertible makes do with a single turbocharger to generate its 245bhp power output and 520Nm of torque. It's still seriously quick. The acceleration from zero to 62mph will take 7 seconds and the top speed of 152mph will be more than sufficient this side of the Bonneville Salt Flats. With the same quantity of torque that you'll get from the 5.0-litre V10-engined M5, the 330d is quite an advert for grasping the black handled pump.

".the BMW 330d Convertible is a car that confounds expectations"

Rival manufacturers would kill for BMW's reputation when it comes to instilling handling balance and driver enjoyment into its vehicles. There was talk, however, that the boys in Munich might have met their match when it came to producing a car with a hefty metal roof that could really shine through a set of corners. There have been some tin-top convertibles that feel like a tent in a typhoon if cornered quickly but the 330d Convertible remains flat and composed. The biggest complement you can pay it is that there's very little difference between the driving experience in this car and the 3 Series Coupe. BMW has achieved this with 160kg of chassis stiffening to compensate for the rigidity lost in shedding the roof. The suspension is more compliant that the Coupe's but that just makes the Convertible more pleasant for cruising about in on a summer's day. The engine is remarkably quiet, even with the top down, so you shouldn't attract attention for the wrong reasons.

This is the facelifted version of the latest 3 Series Coupe so there are a number of visual differences between this and the original folding hard-top version. Most noticeable is the single air-intake sliced in below the front bumper with matt aluminium fins mounted within it. Its effect is to visually lower and widen the car for a more planted and sporty stance. It appears to work. Other features include the revised headlights with LED corona rings and red LED rear lights.

BMW has been selling soft-top 3 Series Convertibles for many years but with this 3 Series, BMW felt the time was ripe to follow a divergent path and get with the technology that's driving huge customer demand - folding hard top roofs. Like all the most modern versions, the BMW system is a three rather than a two-piece system. The advantage of this is that you don't need a distended bottom on the car to accommodate the larger sections of a two-piece roof. The downside of stacking three pieces atop each other instead of two in the boot is that when they're folded, there's not a great deal of luggage space left. With the roof in place, you'll get 350 litres of load space. Fold it down and 140 litres is instantly pared from that figure.

The operation of the roof takes a so-so 22 seconds but there are some real practicality benefits offered. Because of the larger glass rear screen and side windows, visibility has improved by 38 per cent when compared to its predecessor. Not only does this mean that rear seat occupants will feel less claustrophobic, it's also an important safety feature, with cars and bikes less able to sit in your blind spot on motorways.

Capability like that of the 330d Convertible doesn't tend to be cheap and BMW want well over £39,000 for an SE model. Opt for the M Sport and you'll pay another £2,500 for its ground-hugging looks and sporty add-ons. All models get leather trim, automatic headlights and wipers, air-conditioning, parking sensors and electrically adjustable seats. The standard gearbox is a six-speed manual but a clever seven-speed double clutch transmission is also available.

A 330d Convertible requires a significant outlay upfront but from there, ownership costs should prove distinctly manageable. Despite its considerable performance, the car can return saintly economy of 46.3mpg with emissions of 162g/km. Residual values are robust too so you'll be able to claw a greater proportion of the initial cost back when it's time to sell the car on.

With its mix of level-headed diesel pragmatism and convertible joie de vive, the BMW 330d Convertible is a car that confounds expectations. If you still think that convertibles compromise handling for a removable roof and diesels put fun on the back burner in favour of low costs, it's time you caught up with the times. There are few better cars to do that in than this one.

A few years ago, diesel convertibles seemed like a silly idea. It's a credit to BMW's engineering expertise that the 330d Convertible makes you wonder what it was we were worried about.

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